Michael Huber writes:

Maybe a parallel to Germany might help. In Germany, tapping into any
communication not intended by the sender to be heard/read/whatever by
oneself is illegal (regardless of whether there are measures taken to
prevent this) under privacy laws. There are some exceptions, but that's the
general rule. ATC communication is only intended for a limited circle of
recipients. Plane spotters are not the intended recipients, thus, they may
not listen.

If you take that to its logical conclusion, it should be illegal for pilots to
listen to any ATC transmission that isn't specifically addressed to them.

It has nothing to do with perceived professionality of the ATC people, and
everything with protecting the privacy of ATC and pilots.

I'm certain that it has nothing to do with protecting privacy, and everything
to do with protecting incompetence.